- Slides: 25
Basics of Magnetism • North pole, South pole, and magnetic field • Magnets and domains • How magnets pick things up • Wires with current • Whiteboard – direction of B field around wire • Loops • Whiteboard – direction of North pole
Demo - Magnet in dish on overhead Definition of N and S poles Compass on overhead Finding polarity of a magnet Shocking revelation THE EARTH’S NORTH POLE IS A MAGNETIC SOUTH POLE!
For Salt Lake City, declination is currently decreasing at a rate of about 7 minutes of a degree per year. At the bottom of most USGS topographic quadrangle maps is a diagram that shows three north arrows -- true north, grid north, and magnetic north -- and the angles between them. True north (The star symbol in the diagram indicates true north). Magnetic north (MN) shows the direction a magnetic compass would point at the time the map was published. Grid north (GN) The difference between true north and grid north is an inherent effect of transforming the earth's spherical surface to a plane surface.
There is no magnetic monopole Demo Magnet on pivot Demo - iron filings B field is N to S (Field Lines loop)
N How do magnets pick things up? Induced magnetism Distance/Force Demo with compass Magnet S N Magnet S Ferrous material (No induced) N S Induced
Remember electric field + + + - + to - Direction of B is from N to S Demo: Magnaprobe and fixed magnet Remember – B Field Lines: • Leave the N pole • Enter the S pole
Magnetic fields encircle wires Thumb in direction of I, fingers wrap as B (Magnetic field) Demo with Magnaprobe/Giant Solenoid
Whiteboards Direction field around wire 1 | 2 | 3 | 4
Which direction is the magnetic field in front of this wire? I right
Which direction is the magnetic field behind this wire? I left
Which direction is the magnetic field behind this wire? I up
Which direction is the magnetic field around this wire? I ?
Loops of wire act as magnets with a N and S pole: S N Show with giant solenoid
N I S Wrap your Rt. fingers with the current, and your thumb is the N pole, the butt of your hand is the S Pole
why an iron core? Demo
Whiteboards Direction North Pole 1 | 2 | 3 | 4
Where da North Pole? outa da page
Where da North Pole? into da page
Where da North Pole? Current goes up in the front of the coil left side
Where da North Pole? Current goes right in the front of the coil Top
Where da North Pole? Current goes down in the front of the coil right side
Where da North Pole? Current goes left in the front of the coil bottom